I currently am working on a few cherry bowls. I know that cherry will darken upon exposure to sunlight from a maple type color to a darker reddish color. I know this is primarily from exposure to UV light. I finish my bowls with a few coats of Formby's Tung Oil Finish and then after thorough drying, I use my Beall system to polish and wax. Does anyone know of procedures to use to accelerate the rate of darkening. What might be a good UV source that could be used close to the wood to darken it. I have a halogen work light but I don't know the primary wavelengths of emission for those bulbs.
Well, there's that big light in the sky outside - cheap, too. Put them out in the sun for a while.
Halogen won't do much for you. And most lights that would do much are shielded to reduce shortwave UV so they won't hurt people. Skin cancer and itchy eyes both hurt.
You could get a germicidal UV lamp (florescent, usually - seen in things like water filters and cabinets to store safety glasses). Some metal halide or mercury vapor lamps sold in the aquarium trade lack the usual UV shield layer since some UV is good for mimicking sunlight.
A good old fashioned carbon arc light is a wonderful UV source, but not one that's all that easy to find these days. If you happen to have an arc welder and a twin carbon arc torch, that would be the ticket to rapid results - but wear your helmet and leathers, and don't catch the wood on fire.
I suppose tanning lamps would likewise work, and you could get a lot of bowls on a tanning bed if you found a tanning store going out of business.
With any of the lights, you should arrange the lights and bowl to be in a box or cabinet that keeps the light off your skin and eyes, and use safety glasses and gloves/long sleeves if you are rearranging bowls with the lights on. A better box/cabinet design would have a switch that turned them off if the door was unlatched, and shiny reflective insides so you got maximum use from the light.
There are a couple of chemical treatments you can choose from, prior to applying finish: ammonia fuming, or lye. A solution of 1 teaspoon of lye in a pint of water will darken cherry quite satisfactorily. Make sure to wipe it down with diluted vinegar, and again with water, before finishing.
"Ecnerwal" wrote: (clip) A good old fashioned carbon arc light is a wonderful UV source, but not
^^^^^^^^^^^^^^^^^^^^ They used to use carbon arc lights for burning plates in the printing industry--they have been phased out because of the toxic fumes they produce. I think it is hard to get the copper-coated carbon rods they use. When they were used, they were never run more than a few minutes at a time, which I think would be insufficient for your purposes.
Also. if you intend to use any kind of light source, you have the question of how to get even exposure all around the bowl. You would have to rotate it on a spit, or devise a reflective surround for the light and the bowl.
It just don't strike me as very practical.
I think the suggestion to use sunlight makes the most sense.
Not on cherry. Use alkali instead -- even a weak lye solution makes cherry quite dark. Ammonia will darken it also. I haven't tried washing soda yet to see if it has a similar effect, but I imagine it will.
"Leon" wrote: Vivid purple turned brown when turning and sanding a pen..... what kind of
^^^^^^^^^^^^^^^^^^^^^^^ Purple heart is brown when it's cut or turned, but the color returns to the surface on exposure to air. Exposure of the purple surface to sunlight will turn it to an ugly brown. So, after turning a pen, just wait, and don't leave it in the window.
I have heard it both way over the years.... From what I understand it is loke people and will react differently to being handled differently. I have had it go extreme purple when cutting.
I've had PH bleach out brown (certainly seemed to be sun-exposure related, though filtered through two sheets of glass and a coat of finish), but I wouldn't call it an ugly brown - more like brittle, tool-dulling black walnut - ie, pretty good looking, but not as nice to work with as walnut. It's mostly "not purple" rather than "ugly", IMHO. YHO may vary, or not be H. Last I looked the bag of shavings I tucked away in the shed was still nice and purple.
I think internal oils in the silicon based wood turns it purple while a hot bandsaw or sun will dry (evaporate) the surface and turn brown.
Consider Coastal Redwood decks. Pinkish color until it gets boiled in the sun - then it turns a silver gray. Sand off that surface and back in the pink.
Most wood changes color and gets hard in the sun.
I have purple heart tree elements (heavy) and sewing wall hanger. I made some nice file handles out of it and white oak. It was a diagonal layered design - looks like a candy cane of sorts - oiled it and it is in my file drawer with the others. It is large as it holds a 3/4" round wood rasp.
"purple heart will turn purple due to heat or HCL or other acid - if you don't believe me, try it. colors are different but both are arguably shades of purple - the HCL is more red, the heat more blue in my experience
Right pronunciation, wrong spelling: hydrochloric (hydro[gen] + chlor[ine]). Any swimming-pool supply shop will have it, but it may be pretty pricy. It's also available in many hardware stores under the name "muriatic acid" -- same stuff, but usually much cheaper than at a pool shop.
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